Colonization of Pneumocystis jirovecii in Patients who Received and not Received Corticosteroids Admitted to the Intensive Care Unit: Airborne Transmission Approach

Background & objective: Pneumocystis pneumonia (PCP) is responsible for pulmonary infection in immunocompromised patients. This study aimed to investigating the frequency of Pneumocystis colonization in patients hospitalized in the intensive care unit (ICU) and evaluating the relationship between PCP and Pneumocystis coloniza­tion. Methods: In the current cross sectional study bronchoalveolar lavage (BAL)fluids of 100 patients were collected from surgery and neurosurgery ICUs with different underlying corticosteroid therapy conditions. Patients were divided into 2 groups (patients who received corticosteroids and not received corticosteroids). Direct examination on BAL fluids was performed by the Gomori methenamine silver andGiemsa staining techniques. Additionally, 2 filtered air samples of the 2 above mentioned units were collected. A nested-PCR targeted mtLSUrRNA gene and sequencing were used to identify Pneumocystis spp. Results: In direct microscopy, 31 out of 100 hospitalized patients (31%) showed positive results. Twenty-three (46%) of smear positive patients were from the group of patients who received corticosteroid, the other 8(16%) were from the group of patients who didn’t receive corticosteroids (P= 0.001). Pneumocystis jirovecii DNA was detected in 77 out of 100 BAL samples by nested-PCR (77%) in which 40(52%) and 37(48%) samples were obtained from the patients who received and not received corticosteroids, respectively. Pneumocystis genome was found in 1 of the 2 filtered air samples. Conclusion: A significant number of patients who received corticosteroids were also colonized by P. jirovecii that may predispose to PCP or be transmitted to susceptible patients. A significant relationship was observed between the mean hospital stay and detection rate.